The present disclosure is generally related to imaging members, also referred to as photoreceptors, photosensitive members, and the like, and in embodiments to undercoat layers containing metal oxide and electrographic imaging members containing the undercoat layers. The imaging members may be used in copy, printer, fax, scan, multifunction machines, and the like. In embodiments, the methods reduce scratching, abrasion, corrosion, fatigue, and cracking, and facilitate cleaning and durability of devices, for example active matrix imaging devices, such as active matrix belts.
The demand for improved print quality in xerographic reproduction is increasing, especially with the advent of color. Common print quality issues are strongly dependent on the quality of the undercoat layer (UCL). Conventional materials used for the undercoat or blocking layer have been problematic. In certain situations, a thicker undercoat is desirable, but the thickness of the material used for the undercoat layer is limited by the inefficient transport of the photo-injected electrons from the charge generation layer to the substrate. If the undercoat layer is too thin, then incomplete coverage of the substrate results due to wetting problems on localized unclean substrate surface areas. The incomplete coverage produces pin holes which can, in turn, produce print defects such as charge deficient spots (CDS) and bias charge roll (BCR) leakage breakdown. Other problems include “ghosting,” which is thought to result from the accumulation of charge somewhere in the photoreceptor. Removing trapped electrons and holes residing in the imaging members is desirable to preventing ghosting. During the exposure and development stages of xerographic cycles, the trapped electrons are mainly at or near the interface between charge generating layer (CGL) and undercoating layer (UCL) and holes mainly at or near the interface between charge generating layer and charge transport layer (CTL). The trapped charges can migrate according to the electric field during the transfer stage, where the electrons can move from the interface of CGL/UCL to CTL/CGL or the holes from CTL/CGL to CGL/UCL and became deep traps that are no longer mobile. Consequently, when a sequential image is printed, the accumulated charge results in image density changes in the current printed image that reveals the previously printed image. Thus, there is a need, which the present embodiments address, for a way to minimize or eliminate charge accumulation in photoreceptors, without sacrificing the desired thickness of the undercoat layer.
The terms “charge blocking layer” and “blocking layer” are generally used interchangeably with the phrase “undercoat layer”.
In the art of electrophotography, a photoreceptor, imaging member, or the like, comprising a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging the surface of the photoconductive insulating layer. The photoreceptor is then exposed to a pattern of activating electromagnetic radiation such as light, which selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic toner particles on the surface of the photoconductive insulating layer. The resulting visible toner image can be transferred to a suitable receiving member such as paper. This imaging process may be repeated many times with reusable photoconductive insulating layers.
Electrophotographic imaging members or photoreceptors are usually multilayered photoreceptors that comprise a substrate support, an electrically conductive layer, an optional hole blocking layer, an optional adhesive layer, a charge generating layer, and a charge transport layer in either a flexible belt form or a rigid drum configuration. Multilayered flexible photoreceptor members may include an anti-curl layer on the backside of the substrate support, opposite to the side of the electrically active layers, to render the desired photoreceptor flatness.
Examples of photosensitive members having at least two electrically operative layers including a charge generation layer and diamine containing transport layer are disclosed in U.S. Pat. Nos. 4,265,990; 4,233,384; 4,306,008; 4,299,897; and 4,439,507, the disclosures of each of which are hereby incorporated by reference herein in their entireties.
Photoreceptors can also be single layer devices. For example, single layer organic photoreceptors typically comprise a photogenerating pigment, a thermoplastic binder, and hole and electron transport materials.
As more advanced, higher speed electrophotographic copiers, duplicators and printers were developed, the performance requirements for the xerographic components increased. Moreover, complex, highly sophisticated, duplicating and printing systems employing flexible photoreceptor belts, operating at very high speeds, have also placed stringent mechanical requirements and narrow operating limits as well on photoreceptors.
The charge generation layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer. The charge generation layer used in multilayered photoreceptors include, for example, inorganic photoconductive particles or organic photoconductive particles dispersed in a film forming polymeric binder. Inorganic or organic photoconductive material may be formed as a continuous, homogenous charge generation section. Many suitable photogenerating materials known in the art may be used, if desired.
Electrophotographic imaging members or photoreceptors having varying and unique properties are needed to satisfy the vast demands of the xerographic industry. The use of organic photogenerating pigments such as perylenes, bisazos, perinones, and polycyclic quinines in electrophotographic applications is well known. Generally, layered imaging members with the aforementioned pigments exhibit acceptable photosensitivity.
Conventional binders used in electrophotographic imaging members typically contain vinyl chloride. Examples of conventional binders are disclosed in U.S. Pat. No. 5,725,985, incorporated herein by reference in its entirety, and U.S. Pat. No. 6,017,666, incorporated herein by reference in its entirety. Additionally, electrophotographic imaging members may be non-halogenated polymeric binders, such as a non-halogenated copolymers of vinyl acetate and vinyl acid.
Conventional electrophotographic imaging members may have an undercoat layer interposed between the conductive support and the charge generation layer. Examples of conventional undercoat layers are disclosed in U.S. Pat. Nos. 4,265,990; 4,921,769; 5,958,638; 6,132,912; 6,287,737; and 6,444,386; incorporated herein by reference in their entireties.
The appropriate components and processes of the above co-pending applications may be selected for the present disclosure in embodiments thereof. Further, the appropriate components and process aspects of the each of the foregoing U.S. patents may be selected for the present disclosure in embodiments thereof.